Paint or gel coating starting to spider/crack on side

It's called checking/crazing. Keeping it out of the sun is about the only to stop it from spreading further. There is no fix except to replace the siding. Your in the years of the siding that had a defect from the factory in the manufacturing process. Can't remember the name of the company but they are out of business now. Ours is doing it as well and if you look at coaches in the 03 to about 08 build you'll see they all have it on certain manufactured units. The darker colors is where it's most apparent. The surface attracts more heat in those areas and the cracking/crazing begins. I'm not saying to not wax your coach but it will not stop it. Painting is an option but if the shop that knows anything about this problem is honest with you they will tell you that it will return. Most shops suggest a repaint and to use brighter colors in the scheme where heat is a little less apparent. I had a quote from Newmar on ours and it was $28K for a reside and paint. That's not happening. Well good luck with yours and hope you can live with it as there is no real cure.

Put a good synthetic wax on it. Easy to put on. Reapply every six months if the sun is that bad. The only reason it's cracking is because of the lack of wax and the clear coat is cracking. You could have it wet sanded and clear coated again.

Best way to slow it down is get something to shade that area from the sun, than go talk with a paint shop they could tell you want to do best and apply some good wax to this area for now.

Here in Vegas I was looking at a typical RV carport but to block the whole RV from the sun and have my slides out it was going cost a ton of money so I built a shade structure for a lot less $$ and now my RV does not get any direct sun to damage the outside, you need to add some shade material to your RV carport and protect it from the sun.